# 3 week active ferment and Refractometer discrepency?

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#### mthompson

##### Well-Known Member
I've had a beer (cream ale, OG: 1.054) in the primary since 3/1. I went to bottle it last night, and checked the gravity with both a hydrometer and refractometer (to see how close they are).

First, the hydro read 1.019 and the refractometer said a brix of 6.2 (or gravity of 1.005, using MoreBeer spreadsheet). Two days prior it read 7 brix (1.011) and I didn't take a hydro reading that time.....just thought that sounded right.

So, I put that fermenter back, and pulled out the secondary that I was gonna bottle after the first. This beer (OG: 1.036) read 1.012 on the hydro and 5.3 brix (1.012, using MoreBeer).

What is going on? Why is the one beer taking so long to ferment, and why (edit: not is do) do I have these discrepancies between the hydro and refractometer in one beer and not the other?

Thanks,

#### HairyDogBrewing

##### Well-Known Member
No way the beer goes from 1.011 UP to 1.019 two days later.
Change that 19 to a 9 and I might go along with that.

The MoreBeer spreadsheet requires the Original Gravity to calculate Final Gravity from Brix.
It has to estimate how much alcohol is present, which throws off the refraction.
Usually, my beers go from 1.048 (12 brix) to 1.008 (2 Brix) but read 5.5 or 5.6 Brix.

#### TheTower

##### Well-Known Member
I don't use it, but I'm fairly certain refractometers cannot be used with fermented beer. Only useful with wort. I'm hoping someone will back me up because I don't use a refractometer.

OP

#### mthompson

##### Well-Known Member
No way the beer goes from 1.011 UP to 1.019 two days later.
Change that 19 to a 9 and I might go along with that.

The MoreBeer spreadsheet requires the Original Gravity to calculate Final Gravity from Brix.
It has to estimate how much alcohol is present, which throws off the refraction.
Usually, my beers go from 1.048 (12 brix) to 1.008 (2 Brix) but read 5.5 or 5.6 Brix.
I am not saying it went up, but am saying that the brix reading I took three days ago was 7. With the OG of 1.054 (14 brix), the MoreBeer spreadsheet says that it is 1.011 gravity.....that's when I decided it was gOK to bottle.

Then, yesterday right before bottling, I took another brix reading (6.2, 1.006 in MoreBeer) from the sample for the hydrometer reading (1.019).....so something is off.

Except, everything read the same in the second beer (just 15 minutes later): OG: 1.036, FG hydro: 1.012, brix: 5.2 (1.012 in MoreBeer).

Is that more clear?

Thanks,

OP

#### mthompson

##### Well-Known Member
I don't use it, but I'm fairly certain refractometers cannot be used with fermented beer. Only useful with wort. I'm hoping someone will back me up because I don't use a refractometer.
Just have to correct the calculation for the ABV.....then it's close. This is what the MoreBeer spreadsheet does.

#### JVD_X

##### Well-Known Member
Sometimes lots of little bubbles or pieces of yeast/trub can interfere with the refractometer reading.

OP

#### mthompson

##### Well-Known Member
I let the hydrometer sample from the problem beer sit for 15 minutes, made sure I was getting a good sample, and did 3 more readings...all had 6.2 for brix. I will try it again in a few days to see if anything changes.